From: Or Gerlitz <ogerlitz@mellanox•com>
To: Ming Lei <ming.lei@canonical•com>
Cc: Or Gerlitz <or.gerlitz@gmail•com>,
Greg Kroah-Hartman <gregkh@linuxfoundation•org>,
David Miller <davem@davemloft•net>,
Roland Dreier <roland@kernel•org>,
netdev <netdev@vger•kernel.org>, Yan Burman <yanb@mellanox•com>,
Jack Morgenstein <jackm@dev•mellanox.co.il>,
"Michael S. Tsirkin" <mst@redhat•com>,
Don Dutile <ddutile@redhat•com>, Tejun Heo <tj@kernel•org>
Subject: Re: hitting lockdep warning as of too early VF probe with 3.9-rc1
Date: Wed, 17 Apr 2013 18:14:48 +0300 [thread overview]
Message-ID: <516EBC68.1090802@mellanox.com> (raw)
In-Reply-To: <CACVXFVMcgMzwHrvimn2awQZCPP2m=_npTGap-m7Ru+jdCoqcyA@mail.gmail.com>
On 07/03/2013 04:03, Ming Lei wrote:
> On Thu, Mar 7, 2013 at 4:54 AM, Or Gerlitz <or.gerlitz@gmail•com> wrote:
>> On Wed, Mar 6, 2013 at 4:43 AM, Ming Lei <ming.lei@canonical•com> wrote:
>>> You are adding one new PCI device inside another PCI device's probe(),
>>> so the new device will be probed, since PCI probe() is scheduled by
>>> work_on_cpu, then cause flush_work() called inside worker function,
>>> which might be a real deadlock.
>> So if I understand correct, you recommend to somehow avoid this nested probing?
> Yes, you might need to avoid the nested probing in your driver.
>
>>> I am wondering why this commit can cause the problem, since the PCI
>>> device will be probed with its driver if there is one driver for it. There is no
>>> any limit on when the driver should be loaded into system, either before
>>> device is added or after.
>> FWIW to undertstanding the issue - the same driver (mlx4_core) is used
>> by the PF and VF, so the VF driver is already loaded at the time its
>> been added as new PCI device.
>>
>>> From driver core view, looks no wrong things are found.
>> So this got me confused, you pointed on possible deadlock, are you
>> saying the deadlock wouldn't be the result of how the driver code is
>> going nor the commited we bisected?
> My commit only affects the driver loading path, but your warning
> is hit in driver probe path triggered by device addition, so the lockdep
> warning should still be triggered without my commit since the two paths
> are totally independent, right?
If this is the case, I am not sure how come we never saw this warning
before 3.9-rc1 which introduced your commit
190888ac01d059e38ffe77a2291d44cafa9016fb "driver core: fix possible
missing of device probe", any rough guess?
next prev parent reply other threads:[~2013-04-17 15:15 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-05 15:21 hitting lockdep warning as of too early VF probe with 3.9-rc1 Or Gerlitz
2013-03-06 2:43 ` Ming Lei
2013-03-06 20:54 ` Or Gerlitz
2013-03-07 2:03 ` Ming Lei
2013-03-10 15:28 ` Jack Morgenstein
2013-03-10 16:37 ` Greg Kroah-Hartman
2013-03-11 1:26 ` Ming Lei
2013-03-11 20:24 ` Ben Hutchings
2013-04-17 15:14 ` Or Gerlitz [this message]
2013-04-11 15:25 ` [PATCH for-3.9] pci: avoid work_on_cpu for nested SRIOV probes Michael S. Tsirkin
2013-04-18 20:08 ` [PATCHv2 " Michael S. Tsirkin
2013-04-18 21:40 ` Bjorn Helgaas
2013-04-18 21:57 ` Bjorn Helgaas
2013-04-19 14:36 ` Michael S. Tsirkin
[not found] ` <CAOS58YO+uV5KkS=sTP9Y3BPPh1nVnQ06yRyNU8GvEbym7R+X+Q@mail.gmail.com>
2013-04-19 16:39 ` Bjorn Helgaas
2013-04-20 19:05 ` Michael S. Tsirkin
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